Method for treatment of heavy media

ABSTRACT

In heavy media beneficiation magnetite is rinsed from ore fractions and recovered from rinse liquor by magnetic separators. The efficiency of the magnetic separation step is improved by separating the wash liquor in a hydrocyclone into a first fraction substantially free of ore contaminants and a second fraction containing most of the ore contaminants in the wash liquor. The contaminant-free wash liquor is treated conventionally in magnetic separators and the contaminants are recycled to the rinse screens or other suitable separation device.

United States Patent Harrison Feb. 1, 1972 [54] METHOD FOR TREATMENT OF HEAVY MEDIA [72] Inventor: Marvin H. Harrison, Carlsbad, N. Mex.

[73] Assignee: International Minerals 8: Chemical Corporation [22] Filed: Apr. 13, 1970 [21] Appl. No.: 27,811

FOREIGN PATENTS OR APPLICATIONS 792,819 8/1968 Canada ..209/172.5UX 806,394 12/1958 Great Britain ..209/172.5

Primary Examiner-Frank W. Lutter Assistant ExaminerRalph J. Hill Attorney]ames E. Wolber and Peter Andress [57] ABSTRACT In heavy media beneficiation magnetite is rinsed from ore fractions and recovered from rinse liquor by magnetic separators. The efiiciency of the magnetic separation step is improved by separating the wash liquor in a hydrocyclone into a first fraction substantially free of ore contaminants and a second fraction containing most of the ore contaminants in the wash liquor. The contaminant-free wash liquor is treated conventionally in magnetic separators and the contaminants are recycled to the rinse screens or other suitable separation device.

8 Claims, 1 Drawing Figure MAGNETITE BRINE SLURRY MAGNETITE ORE SLURRY PRODUCT MAGNETITE BRINE 56 SLURRY INVENTORJ MARVIN H. HARRISON METHOD FOR TREATMENT OF HEAVY MEDIA Many ores are amenable to beneficiation by heavy media techniques. In such processes the ore is ground to liberation, mixed with a heavy media, and introduced into a separatory vessel, usually a vortex separatory vessel which is typified by the hydrocyclone. The heavy media comprises an aqueous liquor and a very finely divided weighting agent, typically magnetite or ferrosilicon of -200 mesh. The media is adjusted to provide a density of separation in the vortex separator intermediate to the density of the ore constituents to be separated. Thus the ore is separated into a first media-ore underflow fraction containing the heavier ore constituents and a second media-ore overflow fraction containing the lighter ore constituents. These two fractions are separately drained of media, which may be recycled. The ore fractions are then separately rinsed with aqueous liquor to remove the adhering weighting agent, and the rinse liquors are treated in a magnetic separator to recover the weighting agent, magnetite or ferrosilicon, and the aqueous liquor substantially free of weighting agent. The rinse liquors cannot ordinarily be recycled directly into the process for the reason that the density of the rinse liquor is too low to be directly useful in the process. The economics of the process, however, requires that the magnetite or ferrosilicon in the rinse liquors be recovered.

The rinse liquors are contaminated, to some degree, with fine ore constituents. The rinse operation is ordinarily conducted on a rinse screen. Although the ore may be carefully sized prior to introduction into the process, attrition of ore particles in the vortex separator and in the draining and screening operation results in the production of fines which contaminate the rinse liquor. Below a certain level, such contaminants merely remain in the clarified liquor from the magnetic separator. However, wear and discontinuity in the draining and rinse screens usually result eventually in unacceptable magnetic separator performance resulting from excessive ore fines in the rinse liquor.

In accordance with this invention the efficiency of the magnetic separation operation is restored by treating the rinse liquor in a second vortex separator, preferably a hydrocyclone. The density of the rinse liquors is much less than the density of the ore constituents, and accordingly, the ore contaminants in the wash liquor report to the hydrocyclone underflow while the overflow comprises a suspension of the finely divided weighting agent in the liquor. This liquor is suitable for separation in the magnetic separator at high efficiency. The underflow from the hydrocyclone is treated to separate contaminating ore constituents from the weighting suspension. This may be accomplished by means of a fine screen. A1- tematively, the underflow may be recycled to the rinse screens where one of the ore fractions from the initial gravity separation is rinsed.

The FIGURE is a schematic flowsheet of a typical beneficiation process employing the improvements of this invention.

The process of this invention is applicable to the recovery of magnetic weighting agent such as magnetite or ferrosilicon from aqueous media employed in the beneficiation of a wide variety of ores. Only recently, however, have heavy media techniques been adopted commercially to the beneficiation of potash ores. Two such processes are described in Canadian Pat. No. 792,819 and in U.S. Pat. application Ser. No. 851,557, filed Aug. 20, 1969, and entitled Beneficiation of Langbeinite-Containing Ores.

The present invention will be specifically described as applied to a process for the beneficiation of a langbeinite-containing potash ore. it will be understood nevertheless that the invention is applicable to the treatment of other ores. Since the beneficiation of a langbeinite ore is fully described in the aforementioned US. patent application, that process will be described here only to the extent necessary to illustrate the present invention.

Referring to the drawing, 100 tons per hour of an ore containing 20.1 percent langbeinite by weight. 14.5 percent sylvite by weight, with the remainder being a mixture of salts, but primarily halite, is introduced into makeup vessel and mixed with recycle heavy media introduced through line 11. The media comprises -200 mesh magnetite suspended in a brine which is nearly saturated with respect to sylvite and halite and also contains substantial dissolved langbeinite. The media density is adjusted to about 2.20. This langbeinite ore and media in the amount of 360 tons per hour is introduced into hydrocyclone 12 under conditions to separate an underflow fraction containing 19.9 tons per hour of langbeinite and 3.0 tons per hour of other salts, together with 153 tons per hour of media. The overflow from hydrocyclone 12 contains 0.2 tons per hour of langbeinite, 76.9 tons per hour of other salts, and 207 tons per hour of the heavy media. The underflow from hydrocyclone 12 is conveyed by line 13 to drain sieve bend 14 and drain screen station 15 where the heavy media is drained from the ore solids, and thence to rinse stations 16 and 17 where adhering magnetite is removed from the ore solids. Drain station 15 and rinse stations 16 and 17 may be sections of a single vibrating screen. The drained heavy media is collected and recycled by line 11 to makeup tank 10.

The overflow from hydrocyclone 12 is directed via line 18 to sieve bend 19 where media is drained and recycled via line 20. The drained solids are conveyed to makeup vessel 21 and mixed with a second recycle heavy media introduced through line 22. The media density is adjusted to about 2.05. This admixture is introduced into cyclone 23 under conditions to separate an overflow enriched with respect .to sylvite and suitable for further processing, as by flotation to further concentrate the sylvite content thereof. The underflow solids, mainly halite, are eventually discarded as a tailing.

The overflow of cyclone 23 is conveyed by line 24 to drain sieve bend 25, drain station 26, and thence to rinse stations 27 and 28. The underflow of cyclone 23 is conveyed by line 29 to drain sieve bend 30, drain station 31, and to rinse stations 32 and 33. The arrangement for the treatment of the first cyclone underflow and the second cyclone overflow and underflow will be seen to be the same, except as hereafter described.

Brine is introduced through sprays 34, 35, and 36 which are placed above rinse stations 17, 28, and 33, respectively, along the vibrating screens. Rinse brine collected from rinse stations 17, 28, and 33 is conducted, respectively, via lines 37, 38, and 39, to sprays 40, 41, and 42, which are positioned above rinse stations 16, 27, and 32, respectively. Rinse brine, containing substantially all of the magnetite initially adhering to the separated ore fractions after draining, is conveyed by lines 43, 44, and 45 to hydrocyclone 46. This rinse brine is in fact a dilute magnetite suspension, but is contaminated by varying amounts of ore constituents. The actual amount of ore constituent in the rinse brine will be understood to vary depending upon the condition of the various screens as well as upon the degree of care exercised in the initial sizing of the ore, and the extent to which the ore constituents are degraded in size by abrasion. However, the rinse brine introduced to hydrocyclone 46 will typically comprise 375 tons per hour of brine, 103 tons per hour of magnetite, and 10 tons per hour of particulate ore constituents.

The parameters of operation of hydrocyclone 46 are adjusted to provide an underflow fraction which contains substantially all of the particulate ore constituents in the feed to this hydrocyclone. The overflow from hydrocyclone 46 is a magnetite-brine suspension substantially free of particulate ore constituents. This can be accomplished at relatively mild hydrocyclone conditions, and it is preferred to employ conditions no more severe than necessary. This avoids unnecessary enrichment of the underflow with respect to magnetite. Because of the extremely fine state of division of the magnetite, and the relatively coarse nature of the ore particles, it is possible to separate the ore particles from the very fine magnetite without substantially altering the composition of the overflow and underflow brine with respect to magnetite content. Such operation, with nearly complete separation of the ore contaminants, is possible with reasonable control of the input head to the hydrocyclone, and the rates at which meterial is withdrawn from the underflow and overflow of the hydrocyclone.

The overflow from hydrocyclone 46 is conducted via line 48 to magnetic separator 50 where the magnetite is separated as a dense slurry and withdrawn through line 52. Clarified brine is withdrawn through line 54 to the brine pool or for other use. The magnetite slurry is recycled to a makeup tank, not shown, where media of the desired density is prepared to replenish the heavy media requirements at tank 10.

The underflow from hydrocyclone 46 is recycled via line 56 to manifold 58 where it is laid down upon the overflow ore solids from hydrocyclone 23, after draining at drain station 26, but before rinsing at rinse station 27. Recycle of the underflow from hydrocyclone 46 has been found practical because of the low rate of solution of langbeinite in brine and the insolubility of sylvite or halite in the circuit brine. thus, both the potash values and the magnetite in the cyclone 46 underflow are eventually recovered.

Alternatively, the underflow from hydrocyclone 46 can be processed by separate screening to separate the particulate solids content thereof having a size larger than about 68 mesh from the remainder of the suspension. The ore solids-free liquid fraction can be conveyed directly to magnetic separator 50 or can be recycled to hydrocyclone 46 either directly or via the rinse screens. The particulate solids separated from the underflow of hydrocyclone 46 are then preferably rinsed with brine to recover adhering magnetite, and the resulting wash waters recycled directly to hydrocyclone 46 or indirectly through rinse station 16, 27, or 32.

The operation of hydrocyclone 46 and magnetic separator 50 is summarized in table i.

TABLE I Tons per Hour It has been found in operation that under the conditions set forth in table I, if the feed to hydrocyclone 46 was applied directly as feed to the magnetic separator 50, without previous treatment, magnetite recovery in the magnetic separator would be reduced by about 30 percent. The unrecovered magnetite would appear in the clarified brine 54, and would be lost entirely unless this brine were recycled to line 32. if this were done, the presence of this magnetite in the wash brine would result in leaving a substantial amount of magnetite on the ore constituents washed at washing stations 17, 28, and 33, which would again result in a loss of magnetite and also in the contamination of the product with magnetite.

What is claimed is:

1. In the recovery of finely divided particulate magnetic weighting material from a dilute suspension comprising an aqueous liquor, said material and particulate ore constituents of substantially larger size than said material, wherein said suspension is processed in a magnetic separator to produce an aqueous fraction substantially free of said material and a dense aqueous slurry rich in said material, the improvement comprising introducing said dilute suspension into a vortex separatory vessel under conditions to form an overflow containing some of said material and substantially free of said ore constituents and an underflow containing some of said material and enriched with respect to said are constituents, introducing said overflow to said magnetic separator, separating the underflow into a first fraction containing most of the ore constituents thereof and a second fraction containing most of the liquid and weighting material thereof, and rinsing said first fraction with aqueous wash liquor to remove adhering weighting material therefrom.

2. The method In accordance with claim 1 including the step of recycling said aqueous wash liquor to said vortex separatory vessel.

3. The method in accordance with claim 2 in which said second fraction is applied as input to said magnetic separator.

4. The method in accordance with claim 2 including the step of introducing said second fraction as feed to said vortex separatory vessel.

5. In the beneficiation of an ore comprising liberated langbeinite, sylvite, and halite by gravity in a vortex separatory vessel in a liquid medium comprising brine and finely divided magnetite whereby an underflow containing most of the langbeinite in said ore and a first overflow containing most of the sylvite and halite in said ore are separated, with said overflow being separated by gravity in a second vortex separatory vessel in aliquid medium comprising brine and finely divided magnetite whereby a second underflow containing most of the halite and a second overflow containing most of the sylvite in said first overflow are separated, with said underflow, second overflow and second underflow being separately drained of medium and rinsed with brine to recover adhering magnetite, and with the subsequent recovery of magnetite from the rinse brine in a magnetic separator to separate a dense magnetite slurry and a clarified brine; the improvement comprising introducing the rinse brine into a further vortex separatory vessel under conditions to separate a further overflow containing some of the magnetite in said rinse brine and substantially free of particulate langbeinite and halite and a further underflow containing some of the magnetite and most of the particulate langbeinite and halite in said rinse brine, subjecting said further overflow to said magnetic separation, and separating said further underflow into a first solids fraction containing most of the particulate langbeinite content thereof and a second liquid fraction substantially free of particulate langbeinite.

6. The method in accordance with claim 5 in which said further vortex vessel underflow is separated into said first and second fractions by recycling and uniting it with the second vortex vessel overflow at a point subsequent to the draining thereof, but prior to the rinsing thereof.

7. The process in accordance with claim 5 in which said second liquid fraction is recycled as an input to said further hydrocyclone.

8. The process in accordance with claim 5 in which said first solid fraction is rinsed with a rinse brine to recover adhering magnetite and said rinse brine is introduced as feed to said further vortex separator. 

2. The method in accordance with claim 1 including the step of recycling said aqueous wash liquor to said vortex separatory vessel.
 3. The method in accordance with claim 2 in which said second fraction is applied as input to said magnetic separator.
 4. The method in accordance with claim 2 including the step of introducing said second fraction as feed to said vortex separatory vessel.
 5. In the beneficiation of an ore comprising liberated langbeinite, sylvite, and halite by gravity in a vortex separatory vessel in a liquid medium comprising brine and finely divided magnetite whereby an underflow containing most of the langbeinite in said ore and a first overflow containing most of the sylvite and halite in said ore are separated, with said overflow being separated by gravity in a second vortex separatory vessel in a liquid medium comprising brine and finely divided magnetite whereby a second underflow containing most of the halite and a second overflow containing most of the sylvite in said first overflow are separated, with said underflow, second overflow and second underflow being separately drained of medium and rinsed with brine to recover adhering magnetite, and with the subsequent recovery of magnetite from the rinse brine in a magnetic separator to separate a dense magnetite slurry and a clarified brine; the improvement comprising introducing the rinse brine into a further vortex separatory vessel under conditions to separate a further overflow containing some of the magnetite in said rinse brine and substantially free of particulate langbeinite and halite and a further underflow containing some of the magnetite and most of the particulate langbeinite and halite in said rinse brine, subjecting said further overflow to said magnetic separation, and separating said further underflow into a first solids fraction containing most of the particulate langbeinite content thereof and a second liqUid fraction substantially free of particulate langbeinite.
 6. The method in accordance with claim 5 in which said further vortex vessel underflow is separated into said first and second fractions by recycling and uniting it with the second vortex vessel overflow at a point subsequent to the draining thereof, but prior to the rinsing thereof.
 7. The process in accordance with claim 5 in which said second liquid fraction is recycled as an input to said further hydrocyclone.
 8. The process in accordance with claim 5 in which said first solid fraction is rinsed with a rinse brine to recover adhering magnetite and said rinse brine is introduced as feed to said further vortex separator. 